INFORMAT statement is used to define default input format for a variable or a number of variables in sequence at once. See an Example below:
data Name;
informat FirstName LastName $10. n1 5.2 n2 4.3;
input firstname lastname n1 n2;
datalines;
Alexander Robinson 35 11
;Here, two sequential variables FirstName and LastName have the informat parameter of $10 meaning Alphanumeric 10 character length.
n1 and n2 are nuleric variables which have been defined to have informat options of 5.2 and 4.3 . However the input value for n1 is 35 that has only two characters and the output table shows it as 0.35 . In a similar manner where input for variable n2 is 11 it is shown as 0.011 INFORMAT 4.3 is making the value to have 3 digits to the right of decimal point here. While INFORMAT 5.2 made input of 35 to be shown as 0.35.
If you run the code above you will receive following output
Here is a link which would clear some doubts why length and w. informats are not compliant with numeric variable https://stackoverflow.com/questions/50375734/sas-numeric-informat-vs-length